It is known that an o-quinonediazide compound decomposes, upon the irradiation of actinic light, and the diazo group thereof forms a compound having a carboxy group. Therefore, when a light-sensitive layer containing an o-quinonediazide compound is processed by an alkaline developer after image exposure, the exposed portion is removed and the unexposed portion forms an image. Thus, an o-quinonediazide compound is very frequently used as a so-called positive working light-sensitive component, in particular, recently for a light-sensitive layer of a light-sensitive lithographic printing plate precursor or a photoresist composition for etching. In particular, a composition composed of a mixture of an o-quinonediazide compound and an alkali-soluble resin is advantageously used from both economical and practical points of view and a mixture of an o-quinonediazide compound and a novolak-type phenol-formaldehyde condensation resin or cresol-formaldehyde condensation resin is most generally used.
Developers for such an o-quinonediazide-containing light-sensitive layer include an aqueous solution containing sodium tertiary phosphate, sodium hydroxide, sodium silicate, potassium silicate, ammonium silicate, etc., which may be used solely or as a mixture. However, an aqueous solution of sodium hydroxide, sodium tertiary phosphate, etc., is inconvenient as a developer for a light-sensitive lithographic printing plate precursor using a metal support when requiring a considerably long developing time since such a solution shows a strong etching action on metal such as aluminum. Furthermore, when using such a developer the result of development is liable to greatly fluctuate and in an extreme case the image formed is frequently removed even by a light excess of the developing time. Moreover, when such a developer is used, reduction in developing faculty due to repeated use is severe and the number (processability) of light-sensitive lithographic printing plate precursors capable of being processed by a definite volume of the developer is very small.
Therefore, recently, an aqueous solution of sodium silicate or potassium silicate has been relatively advantageously used. This is because the solution has weak etching action to a metal such as aluminum and also the developing property of the developer can be controlled to some extent according to the component ratio of silicon oxide (SiO.sub.2) to sodium oxide (Na.sub.2 O) or potassium oxide (K.sub.2 O) (generally shown by mol ratio of SiO.sub.2 /Na.sub.2 O or SiO.sub.2 /K.sub.2 O) which are the components of sodium silicate or potassium silicate, and the concentrations of them. That is, as the content of SiO.sub.2 increases, the developing power is restrained to increase the development stability and as the content of Na.sub.2 O or K.sub.2 O is increased, the developing power is increased to reduce the development stability. The term "development stability" means the stability of images to a development time and if the content of Na.sub.2 O or K.sub.2 O is increased, the image is liable to be removed in a short period of time.
It is preferable that the processability by a definite volume of a developer is higher as the content of Na.sub.2 O or K.sub.2 O is larger. Accordingly, by increasing the total concentrations of SiO.sub.2 and Na.sub.2 O or K.sub.2 O while controlling the SiO.sub.2 /Na.sub.2 O ratio or the SiO.sub.2 /K.sub.2 O ratio from the aspects of developing power and development stability, a desired processability can be obtained to some extent together with desired developing power and development stability. However, a conventional developer is insufficient with respect to all of the foregoing properties. For example, a developer having a standard developing power tends to lack stability and a developer having a standard stability tends to lack developing power and processability. Also, a conventional developer of this type is not desirable in that since the concentration of the developer is relatively high, the developer is liable to form precipitates and also a large amount of an acid is required for neutralizing the waste solution after use.
The foregoing problems on the developers containing sodium hydroxide, sodium tertiary phosphate, sodium silicate, potassium silicate, etc., are summarized as follows. That is, if the alkalinity of the developer is increased, the developer is superior in developing power and processability but is lacking in development stability and for obtaining high development stability, the alkali concentration must be reduced, which results in reducing the processability of the developer. Accordingly, if a high development stability can be obtained in a state that the developer has a high alkalinity, a developer having excellent developing power, processability, and development stability can be obtained.
As a method of obtaining a high development stability in the state of high alkalinity, a method of adding an anionic surface active agent or an amphoteric surface active agent to a developer is described in Japanese Patent Application (OPI) No. 51,324/'75 (the term "OPI" indicates an unexamined published patent application open to public inspection), a method of adding a water-soluble cationic polymer to a developer is described in Japanese Patent Application (OPI) No. 95,946/'80 and also a method of adding a water-soluble amphoteric high molecular electrolyte to a developer is described in Japanese Patent Application (OPI) No. 142528/'81. However, when these developers are used in an automatic developing machine, they cause undesirable foaming during development.
Also, it is described in Japanese Patent Application (OPI) No. 25,100/'80 corresponding to Canadian Pat. No. 1,145,190 that an ionic compound of a transition element belonging to Groups IIA, IIIA, and IIIb of the periodic table is added to a developer. Such a developer may have an effect of restraining etching of an anodically oxidized aluminum support by a strong alkali but has insufficient development stability.